Definition: In this task, you are given an input list A comprising of numbers and alphabets. You need to extract and sort the unique alphabets in the list. The alphabets in the input list will only be in lowercase. Return -1 if there is no alphabet in the input list.
Input: ['1421', 'f', '6023', 's', '9699', 'l', 'c', '3943', '2311']

c, f, l, s